Orthodontic process and outcome: efficacy studies--strategies for developing process and outcome measures: a new era in orthodontics.

The development of process and outcome measures in orthodontics lends itself to retrospective clinical studies. Once valid and reliable measures have been tested, prospective studies may utilize these measures to assess the quality of orthodontic treatment outcome and the duration and process of treatment. The findings from two retrospective studies comparing the quality of outcome using the peer assessment rating (PAR) occlusal index and duration of treatment are reported. Class I and Class II treatment comparisons indicate the duration of treatment time is increased on average 5 months in Class II, division 1 patients. In the second study, the effect of extraction/non-extraction treatment in a sample that included all types of malocclusion indicates that, on average, treatment time is increased by approximately 5 months when extractions are included as part of the orthodontic treatment plan.